Variable Speed Heating Cooling Pros Cons

Variable Speed Heating and Cooling Pros Cons. Looking to purchase a new heating and cooling system and want to know more about variable speed HVAC systems pros and cons?  Let’s go into some details you might want to consider when looking to purchase a variable speed system, Call D C’s heating & air conditioning at 949-770-9616 today.

Variable Speed Heating and Cooling Pros Cons
Variable Speed Heating Cooling Pros Cons

Variable Speed Heating and Cooling Pros Cons

Lets go over the pro’s first about having a variable speed blower motor for your heating and cooling system. The answer may lie with a variable speed technology central heating and cooling system.

Unlike a base model or single speed HVAC system which cycles ON at 100% then OFF, equipment with variable speed technology may use less energy because it is designed to operate at multiple capacity levels.

An air handler is usually a furnace or a blower coil. Unlike conventional single-speed motors, a variable speed motor runs at a wide range of speeds to precisely control of heated and cooled air throughout the home. ECM are quieter motors and when noise is an issue they will cut the DB’s

The term “Variable Speed” actually refers to the blower motor inside the furnace or air handler. It’s an Electronically commutated motor, or (ECM). ECM’s are DC motors that function using a built-in inverter and a magnet rotor, and as a result are able to achieve greater efficiency than most AC motors.

Variable Speed Heating  Cooling Pros Cons
Variable Speed Heating  Cooling Pros Cons

Variable Speed Heating and Cooling Pros Cons

Now let’s go over the cons.  Theses motors fail a lot and unlike the regular 2 and 3 speed fan motors they are expensive to diagnose and replace. When installing a variable speed furnace or air handler the contractor should test static pressures in supply and return to prevent premature motor failure.  Always replace your air filter every 3 – 6 months if using 1 inch air filters. If you are using the 4 – 5-inch filters once a year,

Most variable speed motors use different transformers and more control boards to make the motor work.  I have replaced many defective variable speed motors this year and expect a lot more.

These new variable speed motors are interesting and might be an energy saving way for the future but at this point as a mechanic I am seeing failure and issues with the motors and the electrical PC boards to run it.

If you do not replace or clean your air filter regularly you will burn this motor up. Most failures are caused from neglect.

Variable Speed Heating  Cooling Pros Cons
Variable Speed Heating  Cooling Pros Cons
variable speed heat pump worth it

Variable Speed: Variable speed compressor technology allows the unit to run at the speed that best meets your comfort needs coupled with energy-efficient operation.  Down fall is expensive repairs.

 Are variable speed air conditioners worth it?

Right now my opinion on variable speed air conditioning is not worth the energy savings and we are seeing motors and the electronic boards failing. These motors and boards are expensive to repair or replace.  Sure, the noise level and electrical saving is a plus. Read my 5-star air conditioning reviews for Orange County, California CA.

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8 responses to “Variable Speed Heating Cooling Pros Cons”

  1. Carlos Rivera

    Hi Chad,
    I live in Brandon, FL. We opted to go through Home Depot to ensure warranty. They subcontracted out to a company called And Services. We purchased a variable speed Daikin. From day one they haven’t been able to get it to work correctly. They’ve swapped out the thermostat, the board and even the entire unit. It keeps throwing a code 54. Problems having to do with the EEV. After numerous codes, the system stops working and the only way to get it to work is to turn the AC breakers on the panel off and on. The system will continue to throw the same code 54 and eventually turn off again. Now we’ve agreed to swap it out for a 3rd unit, but a Bryant this time. And although the handler is a variable blower, the condenser is only a one speed. Living in FL, I really would like a variable speed condenser as well. But the company says that the Bryant Evo system is going to have the same issues I have with the Daikin system. Are they correct or should I seek a different company?

    Reply
    1. Chad

      Hi Carlos,
      I love the Bryant products. Carrier, Bryant and Payne are the best in my book. I installed a several Bryant Evolution units here in Orange County California. We do not have a humidity problem but The evolution unit is made to control your comfort in your home. They are not cheap but getting up to 28 SEER is huge on energy efficiency The compressor is a variable speed running from 20% to 100% as your demand changes. Lets say you set your thermostat for 72 degrees and set your humidity to 45% the system changes the fan speeds while the compressor will also use its 8 different speed to keep your temperature and humidity constant what you set it for.

      I have never liked Daikin or Goodman products. They are cheap and nothing but issues.

      When you use the Bryant equipment make sure your contractor matches the furnace and condenser to achieve the best performance. I only use ADP brand evaporator coils for my installs because quality is key. Here is a link to the Bryant evolution series https://www.bryant.com/en/us/products/air-conditioners/186cnv/ https://www.bryant.com/en/us/about-bryant/media-center/

      Reply
  2. Karl

    Hello,

    This article is interesting but it is now about 3.5 years old. Has anything changed in the technology since then to change your opinion or observations?

    Thank you

    Reply
    1. Chad

      Great question. As far as furnace and air handlers in California are almost all variable speed blower motors. Yes the variable speed has some good points like quite operation and also energy savings. The issue we have been seeing is failure and properly diagnosing the issue. The question is when your blower motor goes out is the motor bad or the board. Most HVAC companies will replace both. These motors and boards are still really expensive to replace. If you are asking about variable speed compressors and 2 stage cooling we can go over that also. Most issues I have seen so far is the installation company did not wire the thermostat or system for a 2 stage system either heating 2nd stage or cooling 2nd stage. This requires extra low voltage wires and many homes have been pre-wired with 4 or 5 wires only. If you have a 2 stage furnace or heater your thermostat must have a wire on w1 and also w2 if you have a 2 stage air conditioner you need a wire on y1 and y2 on your thermostat other wise your heating and cooling system will not be energy efficient and working properly.

      Please feel free to post any question I am here to help.

      Reply
      1. Dave

        My partner and I are needing to replace our AC/Furnace as both are old, and he is looking with an eye towards a variable set from Lennox..I’m a bit leery as they’re over 5-7K more than other estimates we got, which I was looking at 2 stage American Standard from another estimator…how long do the circuit boards and motors on the variable AC/furnaces seem to last and on average, what is the cost to replace?

        Reply
        1. Chad

          Hi Dave,
          First buying a brand is important. Lennox is 1 of my top 5 choices for heating and air conditioners. With 30 years experience working on all brands I am not biased about what’s hot and what’s not. Each contractor or company has different prices for new equipment sales. Last year in Orange County CA my average prices for a complete Payne furnace, ADP evaporator and Payne 14 SEER condenser ran $8750.00 out the door. Bryant furnace ADP evaporator and 14 SEER condenser was $9450.00 out the door. I am a huge fan of Carrier, Bryant, Payne. The copper condenser coils last for years. This year I removed many American Standard and Trane units because the aluminum condenser coil leaked. Yes these units only lasted 5-7 years. Variable speed motors and boards. To answer this question how long will they last? Ok these motors fail from not replacing the air filter regularly – Poor ducting restrictions- High MERV air filters – or just a cheap brand. Variable motors are not as forgiving as our typical 4 speed motors. Yes we only use 2 speeds heating and cooling in a typical furnace. What is the cost to replace a variable speed motor? Some brands you have to use the OEM motor and we cannot just use an aftermarket. Costs for just the motor alone compared to a regular 4 speed is going to run 4X more money. This will not include the boards. I am sure most experienced HVAC technicians would want to replace all the boards because it is hard to return a new motor that just burned up due to using old boards. If you decide to go with a variable speed furnace always have your technician check the CFM and Velocity in supply and returns.

          Reply
          1. Scott

            I am just in the process of replacing my 11 year old Lennox unit that has given me nothing but problems. The air handler motor has been replaced once every 3 years at $600 – 800 and the evap coil was replaced last year at a god awful price. Lennox parts are hard to come by in my area in the southern US for some reason. I am leaning towards a simple non-variable speed motor with copper coil. I’m wondering how much more my AC bill will be with such a configuration, but to me reliability is worth the extra amount, especially in the heat of the summer where I live.

          2. Chad

            Hi Scott Thank you for your post. Lennox units are nice and come with a great warranty. When you have a variable motor we have to consider this. Is our air return proper sized for the ECM motor? Varible ECM motors need low static pressure and really clean air filters to make sure they last. ECM variable motors fail for these reasons and an inexperienced HVAC technician will just replace and charge you. Why did you go through 3 motors? You have an issue with the return or even the supply static pressure but to know this the technician or installer should have measured the static pressure during install or even after replacing the first motor. Did you go with a larger system in your home that was originally installed? Honestly you should be getting 20-25 years from your Lennox system in my opinion. For evaporator coils I only use Advanced Distributor Products or ADP. ADP is the best evaporator in the heating and air conditioning world in my opinion, registered you get a 10 year warranty. I would probably suggest you had a bad installation and also a technician that just replaced the motor without looking into why it failed.

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